linux-kernel - Re: [PATCH] m68k: Use generic strncpy_from_user(), strlen_user(), and strnlen

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Date:	Wed, 6 Jun 2012 19:46:02 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Greg Ungerer <gerg@...pgear.com>
Cc:	Philippe De Muyter <phdm@...qel.be>,
	Greg Ungerer <gerg@...inux.org>,
	linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] m68k: Use generic strncpy_from_user(), strlen_user(), and strnlen_user()

Hi Greg,

On Wed, Jun 6, 2012 at 8:31 AM, Greg Ungerer <gerg@...pgear.com> wrote:
> Yes, looks like that should have a "|| defined(CONFIG_CPU32)".
> (According to the CPU32 reference manual words and long words must
> be aligned on word boundaries.)
>
> I think something like CONFIG_CPU_HAS_NO_UNALIGNED makes sense.

OK, doing that now...

Then I saw arch/m68k/lib/memcpy.c.

commit f230e80b423f6cb002015ab4771c06a53d5a2287
("m68k: fix memcpy to unmatched/unaligned source and dest on 68000")

| The original 68000 processors cannot copy 16bit or larger quantities from
| odd addresses. All newer members of the 68k family (including ColdFire)
| can do this.

So all Coldfires can do unaligned _reads_, but not unaligned _writes_
(exceptions below)?

>>> I also think that the Coldfire 5272 can do unaligned accesses, but I
>>> cannot test that at the moment.
>
>
> According to the MCF5272 User Manual, "it supports misaligned data
> accesses ...". So it looks like it does.
>
> Having a CONFIG_CPU_HAS_NO_UNALIGNED looks like a really good solution
> then. We need to be able select it as required on individual CPU types.

For now, I just make COLDFIRE select it, but we can move it to the individual
CPU types later.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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